Dental casting machine



y 1930- L. c. BURGARD 1,757,991

DEI JTAL CASTING MACHINE I Original Filed June 16, 1927 5 Sheets-Sheet 1 38 G1 a a9 2 INVENTOR.

Louis C. Eurgard,

A TTORNEY.

May- 13, 1930.

L. C. BURGARD DENTAL CASTING MACHINE 3 Sheets-Sheet 2 Original Filed June 16, 1927 y 1930- i L. c. BURGARD 1,757,991

DENTAL CASTIfiG MACHINE igirial Filed June 16, 1927 s sheets-sheet 3 INVENTOR. Louis C. ELI/"yard,

ATTORNEY.

Patented May 13, 1930 PATENT OFFICE LOUIS c. BURGABD, or LOUISVILLE, xnNrocxY DENTAL CASTING MACHINE Application filed June 16, 1927, Serial I'm-199,305. Renewed September 20,

My invention relates to dental casting machines. r

As is well known, dental castings, such as inlay fillings and the like are produced by first -forming a pattern from wax. This pattern is formed directly within thecavityto be filled, and is subsequentlyremoved from the cavity. The wax pattern, with other proper forming elements, is next imbedded within a body of investment material, contained within a flask or mold. The flask holding the investment material is next heated, with the result that a portion of the wax is evaporated and the remainder liquefied and absorbed by the porous material, producing a cavity in the investment material of the proper size and shape. After this, the other pattern forming elements are removed, producing in the body of the-investment material a mold cavity, a cup or chamber above the same for the reception of gold or other metal and a conducting sprue leading from the cup to the mold cavity, for the flow of the molten metal. I F After the mold cavity has thus been prepared, a mass of gold or other suitable metal, of suitable size, to'form the desired casting, is placed in the cup, and the flask is heated the metal molten. I

Owing to the relatively small size of the sprue, the molten metal can not properly flow into the 'mold cavity,andmeanshavebeen prometal. Ithasbeen proposedto create a suction or vacuum beneath the mold cavity, thus draw ing the molten metal downwardly into the cavity, and it has also been proposed to apply- 4 pressure above the molten metal, thus forcing it to a sutficiently high temperature to rendervided to efli'ect this prpper flow of the molten downwardly into the mold cavity. It is genleakage occurs when the pressure is applied to the molten metal, rendering it difficult or impossible to subject the molten metal to a proper constantpressure. In accordance with my invention, I providea casting machine so constructed that desired pressure is applied to the top of the molten metal, to force the same downwardly into the mold cavity. The pressure is applied to the metal without any perceptible loss of pressure, 0

whereby the selected pressure may be employed. This is effected by providing selfadjusting means for effecting a proper contact between the pressure supplying element and the flask, 'whereby an air-tight joint is obtained between these parts. The machine is also preferably so constructed that the valve of the pressure supplying element is automatically opened after an air-tight joint has been eifected between the pressure supplying element and flask, The'pressure supply ing element is preferably mounted upon a lever adapted to swing downwardly toward the flask, and means are provided to automatically lockthe lever in the lower position, holding the pressure supplying element in contact with the flask.- The base of the machine preferably. constitutes a pressure storage tank and all operative parts are mounted' ipon or carried by the base, whereby. the machine is balanced and maybe used without the necessity of attaching the base to a table or a support.

I In the accompanying drawings, forming a part of this specificat1on,and in which like 5 numerals are em loyed 'to designate like parts throughout he same:- 1

Figure 1 is a side elevation of a casting machine embodying my invention,

Figure 2 is a plan view of the same,

Figure 3 is a central vertical longitudinal section through the same,

Figure 4 is a transverse section taken on line 4-4 of Figure 1,

Figure 5 is a detailed section through the lever, showing the pressure supplying element in the projected position,

Figure 6 is a transverse section taken on line 66 of Figure 5,

Figure 7 is a bottom'plan view of the cap the plunger 17 compressed air will be stored included in the pressure supplying element, Figure 8 is a plan view of the machine, parts omitted, and parts in section,

Figure 9 is a perspective view of a table, Figure 10 is a similar view of a holding frame, and

Figure 11 is a similar view of a flask holder. In the drawings, wherein for the purpose a of illustration, is shown a preferred embodi- .ment of my invention, the numeral 10 designates a pressure stora e tank or chamber, constitutin the base 0 the machine. This tank is preferably horizontally arranged and is equipped at its ends with depending legs 11, which may be apertured so that they may be screwed or attached to a' table or the like,

but this-is ordinarily not necessary, as the.

machine is well balanced, whereby it may be used without such attachment. The tan 10 is provided at its forward end with a vertical. chamber 12, in free communication in a cap 20. .The opening 19 is larger in diameter than the rod 18 to permit of the passage of air through the opening 19. The

rear end of the rod 18 is equipped with a knbb or handle 21. The plunger 17 is equipped with the usual check valve to permit of the air passing through the plunger upon its rearward stroke but closing upon the forwardstroke of the plunger. At its -forward end, the pump cylinder is equipped with a check valve 22, of any well known or preferred type, which check valve opens forwardly. The invention is in no sense restricted to the particular type of pump shown. It is obvious that by reciprocating within the tank 10. The forward wall of the chamber 12 is preferably rovided with a screw-threaded opening close by a plug 23, whereby an air prwsure supply line or pipe -1nay be placed in communication. with the tank 10. A- pressure gage 24 is also mounted upon-the top of the chamber 12 and in com- ,munication with the interior thereof.

The tank 10 has its intermediate ,to tion in the form of a flat wall 25 and ollow vertical lugs 26 are cast u on the sides of thetank 10, adjacent to the ranged above the flat wall 25 is a self-adjustingsupport or tray 27, preferably provided with apertures .28. This self-adjusting support :or tray is provided centrally of its side ment 56 and por- 1: wall 25.v Ar-.

edges with lugs 29, preferably cast integral therewith, and these lugs have screw-threaded openings 30 formed therein, to engage with the screw-threaded ends of bolts 31, having their heads arranged beneath the hollow lugs 26, as shown. The bolts 31 extend through openings 32, of greater diameter than the bolts, thus permitting of lateral movement of the bolts, within limits, in all directions. Arranged within the hollow lugs 26 are suitably stiff compressible coil springs 33, engaging the lugs 29, and retaining the self-adjusting support 27 spaced from the wall 25. This is a very important feature .of the invention, as the springs constitute the yielding means for supporting the self-adjusting support or tray, which is thus capable of tilting in all directions.

Arranged upon the self-adjusting support ing element or tray is a table 34, the legs of which are adapted to be held within lugs 35, cast upon the corners of the self-adjusting supporting element or tray. Arranged upon the top of the table 34 is a holding frame 36 having a flange 37, engaging a flange 38, cast upon the top of the table and a flange 39, engaging between lugs 40, cast upon the top of the table. The holding frame is provided with circularly curved recesses 41, to engage the edges of a cylindrical flask holder 42. This flask holder has a recess 43 in its top, for receiving the bottom of a flask 44, holding the investment material 45.

The mold cavity 46 is produced in the investment material, and has communication with a sprue 47, leading to a cup or chamber 48 for receiving the metal, such as gold.

The numeral 49 designates a movable supporting member, preferably in the form of a lever, provided at its rear end with a pistolgrip handle 50. The'forward end of the lever is forked forming handle sections 51, which straddle the top of the air chamber 12; The vforward end of these handle sections are apertured to pivotally receive a bolt '52, extending through a solid portion 53,

formed in the top of the chamber 12. The bolt 52-may be adjusted or tightened up to provide sufficient friction whereby the lever 49 will remain in different raised positions, when shifted thereto.

The lever 49 is provided. intermediate its ends with a transverse collar 54, preferably integral therewith. The collar 54 carries 9. lug 55 integral therewith, which is received within the rear forked end of a locking eleivoted thereto by means of a bolt 57. The l 58, adapted to'contact with an ad'ustable stop 59, in the form of a bolt, screw-t eaded ocking element 56 has ahead withm an opening 60, formed in a lug 61.

The bolt 59 carries a locking nut 62, as shown. When the lever 49 is moved to the lowered position," the locln'n element 56 automatically engages behin the stop 59, thus locking the lever in the lowered position. By a slight depression of the lever, thelocking element 56 may be raised out of engagement with the stop 59.

' The device embodies a pressure supplying 64 and serves 'to urge the tube 63 down-,

wardly, which movement is limited by a sto rangement is such that an air-tight joint is effected between the ball and socket elements, and an universal joint is effected between the cap 68 and the tube 63. The cap 68 is provided upon its lower face with an annular recess, receiving compressible material may be employed. The ca 68 is proyided with an upstanding stem 72, rigidly attached thereto and this" stem extends into the bore 65, but is .of smaller diameter, to permit of the passage of air thereabout,

and the stem 72 serves to limit the pivotal movement of the cap 68 with respect to the tube 63.- Surrounding the stem 72 are apertures 73, leading into the bore 65.

The tube 63 is provided at its upper end witha valve, including a casing 74, having a tapered transverse opening for the reception of a tapered valve element 75, held upon its seat by a spring 76. This .valve element has a transverse port 77, adapted to be moved into/and out of registration with the bore of the tube 63, as is obvious. The valve element is tufned by means of a crank 78, rigidly attached to one end thereof, having pivotal connection with a link 79, extending downwardly for'pivotal connection with the lever 49, as shown at 80. A flexible tube 81 leads into the top of the valve casing 74 and its opposite. endleads into the top of the chamber 12, whereby the valve casing and chamber are in communication.' When the lever 49 is partly or wholly elevated, the spring 66 projects the tube 63 downwardly with relation to the lever maintaining the valve element 75 closed, as clearly shown in Figure 5. The tube 63 must be moved upacking 71, preferably asbestos, although ot er suitable wardly with relation to the leve'. 49,- for a I considerable distance before the; valve element 75 is shifted to the partly orcompletely open position.

The operation of the machine is as follows: The mold cavity46 is formed in the investment material 45 within the flask 44, with the cup 48 and sprue 47, as explained. The flask 44 is suitably heated, to melt gold or other metal within the cup 48 and then placed upon the holder 42, ,but the flask maybe heated when mounted upon'the machine if desired.

With the parts in the position as shown in the drawings, the lever 49 is swung downwardly with a suitable air pressure within the tank 10, which is preferably about five pounds.

p When the cap 68 approaches the top of the collar 67, arranged above the collar 54. The.

numeral 68 designates a cap provided upon flask 44, the compressible washer 71 engages with the top of the flask, forming an air-tight joint therewith. Pressure upon the lever 49 ,will cause the self-adjusting supporting elementor tray 27 to tilt in the desiredidirection, and also the cap 68 to tilt in any desired direction, whereby a close uniform contact is afforded between the top of the flask and the washer 71, throughout their entire areas with the result that an air-tight joint is effected. This is very important as leakage of air will materially interfere with the completely successful operation ofthe machine. It is thus seen that the flask is supported in a manner whereby it may tilt, within limits, in all directions, while the cap 68 may also tilt within limits in all directions. Further downward pressure upon the lever causes the lever to move downwardly with relation to the tube 63, with the result that the valve element 75 is through the tube 81, tube 63, and through the ports 73 into the cup 48, forcing the molten -metal through the sprue 47 into the mold cavity 46. In this manner, aselected pressure is directly applied to the top of the molten metal, which is rendered possible by the fact that the air does not escape between the contacting parts of the flask and the pressure supply element. When the operation is completed, lever 49 is slightly depressed, and the locking element 58 raised, to clear the stop 59, subsequently to which the lever 49 will be'released. a

It is to be understood that the form of my invention, herewith show and described, is to be taken 'a'sa preferre example of the same, and that varirius changes in the shape, size and arrangemen of parts-maybe resorted to without departing from the spirit of my,

invention, or

, sure now'passes from the air chamber 12 Having thus described my invention, I claim:

1. In a dental casting machine, a support for a flask, a lever pivotally connected with the support above the flask by means of a fixed pivot, an element carried by the lever and having a part to enga e with the flask, and a locking element movably mounted upon the lever and separate from the fixed pivot and adapted todetachably engage with a part of the support to hold the lever in the inner position when shifted thereto. 0

2. In a dental casting machine, a support for a flask, a vertically swinging lever pivoted to the support abovethe flask, a pressure supply element carried by the lever and having a part toengage with the flask, and a gravity operated locking element separate from the pivot of the lever and pivotally mounted upon the lever and adapted to auto matically detachably engage behind a part of the support to hold the lever in the lowered position when shifted to the same.

3. In a dental casting machine, a pressure storage tank serving as a base and provided with an upstanding part, said base being adapted to hold a flask, a lever pivotally connected with said upstanding part and arranged above the flask, a pressure supplying element carried by the lever to engage the flask, means of communication between the pressure supplying element and the pressure storage tank, and a locking element separate from the pivot of the lever and pivotally connected with the lever and adapted to detachably engage with a part of said upstanding part to hold the lever in the depressed position when. moved to the same. 7

4. In a dental casting machine, a pressure stora e tank serving as a base which will not readi y tip over and having a part to receive thereon a flask, a lever pivotally mounted upon the base and having a transverse collar, a tube slidable within the collar, a spring to oppose the sl'idin movement, of the tube in one direction, a ask engaging member carried by the tube, a turning valve'connected with the tube and having a crank, a link connecting the lever and crank, and means of communication between the tube. and tank.

5. In a dental casting machine, a support, a self-adjusting supporting member mounted upon the support and provided near its corners withiupstanding lugs, a table having legs to engage within the lugs and provide 'upon its top with lugs, a holding frame having lugs to interlock with the lugs upon the top of the table, a flask holding member-haw ing its bottom adapted for insertion within the holding frame and provided upon its top with a recess to receive the flask, and means to supply pressure to the top of the flask.

6. In a dentalcasting machine, a generally horizontal tank serving as a base, said tank having an upstanding part, a flask supporting member arranged near the upper portion of the tank, a elding universal connection between the g1 sk supporting member and tank whereby the member may partake of universal movement, a lever pivotally connected with said upstanding part, a tube carried by the lever, a. flask engaging element carried by the tube, a flexible tube connected with the first named tube and having vconnection with said tank, a valve controlling the passage of fluid through the first named tube and a locking element pivoted upon the lever and having its free end arranged to detachably engage the upstanding part. V

7. In a dental casting machine, a support for a flask and having an upstanding part, a lever pivoted to the upstanding part and adapted to be swung toward and away from the flask, a flask engaging element carried by the lever, and a locking element separate from the pivot of the lever and bodily mounted upon the lever to be shifted therewith, said l'ocking element being movable with relation to the lever and having airee end adapted for detachable-engagement with the upstanding part.

8. In a dental casting machine, a support to receive a flask thereon, a lever pivoted to the support and adapted for swinging movement' toward and away from the flask, said lever having a transverse opening, a tubular element longitudinally movably mounted within the transverse opening, yielding means to oppose the longitudinal movement of the tubular element with relation to the lever, a turning valve connected in the tubular element, a crank connected with the turning valve, 9. link connecting the crank and lever, and a flexible tube connected with the tubular element. 7

9. In a dental casting machine, a storage tank having an upstanding part, saidstorage tank having means thereon for supporting a flask, a lever pivotall connected with the upstanding part, a tu ular element extendmg therebyv and movable lon 'tudinally with relation to the lever, a fl engaging element carriedv by the tubular element, a. spring to oppose the longitudinal movement of the tubular element with relation to the lever, a tapered turning valve connected in the tubular element, a spring tending to hold the tapered turning valve upon its seat, a crank connected wth the turmng valve, a link contransversely of the lever and carried necting-the crank and lever, and a flexible ing part carried by the tank, a lever pivotally connected with the upstanding part, a tubular element carried by the lever and ex- ,tending transversely thereof and movable longitudinally Wit-h relation thereto, a flask engaging element carried by the tubular element, yielding means to oppose the longitudinal movement of the tubular element with relation to the lever, means of communica-L. tion between the tubular element and tank,

a pivoted valve carried by the tubular ele- 'm'ent for controlling the passage of fluid 7 through the tubular element, and automatic means to operate the valve upon the move- '1nent of the lever with relation to the tubularelement. i

11. In a dental casting machine, a generally horizontal tank having a tubular upstanding part in communication with said tank, said tank having aflask supporting part arranged near its top, said tank serving as a base which will not readily tip over, a lever pivotally connected with the upstanding part, a tubular element carried by the lever and extending transversely thereof and movable l mgitudinally with relation to the lever, yielding means to oppose the relative longitudinal movement of the tubular element, a flask engaging element carried by the tubular element. a flexible tube connected with the tubular element and with the upstanding tubular part, a pivoted valve con trolling the passage of fluid through the tubular element, means connecting the pivoted valve and lever whereby the pivoted valve is operated upon the movement of the lever with relation to the tubular element and means to lock the lever in the lowered position.

p 12. In a dental casting machine, a generally horizontal tank serving as a base and having an upstanding part, said tank having a part for supporting a flask, a lover, a fixed pivot connecting the lever and upstanding 5 part, a tubular device carried by the lever and embodyinga flask engaging part, means of communication between the tubular device and said tank, and a locking element having one end pivotally connected with the lever at a point spaced from the fixed pivot of the lever and having its free end adapted to be moved into and out of engagement with said upstanding part. 1

In testimony whereof I afiix my signature.

LOUIS C. BURGARD. 

